1. Field of the Technology
The present invention relates to information interaction between Access Terminal (AT) and High Rate Packet Data (HRPD) network, and more particularly, to a method for establishing HRPD network packet data service in a 1x network.
2. Background of the Invention
Code Division Multiple Access (CDMA) 2000 1x network has widespread users. It mainly provides circuit-switched voice service and medium and low rate data service. CDMA2000 1x EV-DO, also called as HRPD, is designed to optimize data applications. The peak data rate of the HRPD Release A reaches 1.8 Mbps on reverse link and 3.1 Mbps on forward link. Closed-loop rate control and capacity enhancing scheduler are key characters to the outstanding performance of the HRPD which transfers data to every user at highest possible rate in burst mode. In other words, it can dynamically select modulation mode and transmission period according to channel conditions to obtain the best performance.
The HRPD Release A also provides enhancement for other features including Quality of Service (QoS), instant multimedia service, Location Based Service (LBS), equalizer, receiving diversity, Voice over IP (VoIP) and multi-carrier. QoS allows the HRDP to handle different applications, such as VoIP and video phone with different methods, so that operators may set different charging rate according to data flow and QoS level.
The HRPD may be used to construct a wireless mobile data network independently or hybrid with the CDMA 1x to complement each other so as to fulfill the function requirements set by International Telecommunication Union (ITU) on 3G systems. As the 3G service market has not been matured, and in consideration of network construction cost, the first phase of the HRPD network construction usually adopts hot spot coverage. Thus the problem of service handoff between the CDMA 1x and the HRPD network emerges on the edge of the HRPD network. And at the same time, within the HRPD network, the same problem is brought out by load adjustment between the CDMA 1x and the HRPD network. Hence research on seamless service handoff between the CDMA 1x and the HRPD network is needed. Seamless handoff means extremely short service interruption during handoff, thus the two networks may complement each other while ensuring user satisfaction.
An AT does not occupy any wireless traffic channel in an HRPD network, yet it maintains a Point-to-Point Protocol (PPP) logic connection to a Packet Data Serving Node (PDSN) which keeps an A10 connection to a Packet Control Function (PCF). This is called a dormant packet data session between the AT and the HRPD network. When the network wants to send data to the AT, and if the AT is monitoring the HRPD network, the AT actively initiates a connection establish request to activate the packet data session after receiving a Page message issued by an Access Network (AN). And the AN assigns a wireless traffic channel to the AT and establishes a cable connection, i.e., an A8 connection, then transmits data to the AT. If the AT is in service in the 1x network, the HRPD network requests the 1x network to send a Page message to the AT, then the AT decides by itself whether to switch to the HRPD network to receive data. When the AT wants to send data to the HRPD network, it activates the packet data session. And after the data transmission is completed, when no data interaction goes on between the AT and the HRPD network for a certain period of time, the packet data session is returned to the dormant state. A dormant handoff refers to a process of transferring, due to the mobility of the AT, HRPD session information from a source AN PCF to a target AN/PCF in preparation for packet data service activation. The HRPD session information includes an HRPD air interface protocol attribute value and a relevant public data value. The active state refers to a state in which the service data are transmitted. During the transmission, an A10 connection handoff may be triggered, wherein the A10 connection is a connection between the HRPD network and the AN/PCF, i.e., a new connection is established while the old connection is released.
As shown in FIG. 1 and FIG. 2, there are two methods to connect the HRPD network and the 1x network, and the two methods may co-exist. On the HRPD network side, there is a PDSN, a PCF and an AN. On the 1x network side, there is a Mobile Switching Center (MSC) and a Base Station Controller (BSC). In the first method, the HRPD network and the 1x network are connected through signaling interface A1/A1p. The A1 interface is based on circuit connection and the A1p interface is based on IP connection. And the signaling interface A1/A1p is mainly used for transmitting 1x circuit-switched service related signaling. In the second method, the HRPD network and the 1x network are connected through a signaling interface A21 which is mainly used for transmitting 1x air interface related messages when the AT is in an HRPD network service.
For an HRPD/1x dual mode AT with a single stand-by mode, it is impossible to enable two wireless interfaces at the same time, which brings difficulties to handoff between networks. It will be advantageous for the seamless handoff between the 1x network and the HRPD network if the AT can establish a packet data service in the HRPD network by virtue of the 1x network wireless interface when working in the 1x network.
When there is no packet data session between the AT and the HRPD network, the process of establishing a packet data service by an AT with an HRPD network in the 1x network includes the steps of:
1. establishing a channel on the 1x network air interface to bear information flow between the AT and the HRPD network when the AT needs to establish a packet data service;                2. establishing an HRPD session between the AT and the AN, including Unicast Access Terminal Identifier (UATI) assignment, session negotiation, and possibly access authentication, etc.;        3. assigning a wireless traffic channel;        4. establishing a connection between the AN and the PCF and a connection between the PCF and the PDSN;        5. establishing a PPP connection between the AT and the PDSN, maybe involves a Mobile IP (MIP) registration.        
The method described above is used for establishing a packet data service by an AT in the 1x network with an HRPD network when there is no packet data session between the AT and the HRPD network. The method, however, does not give a solution to establish a new HRPD service when there is an existing dormant session.